There are power converters which are to be mounted in electric vehicles or hybrid vehicles and in which a plurality of semiconductor modules are connected to other electric devices through bus bars. For instance, Japanese Patent First Publication No. 2006-295997 discloses a power converter with a single bus bar which is formed by punching out a metallic plate and equipped with a plurality of connecting terminals joined to connecting terminals of a stack of semiconductor modules.
However, the above described power converter is designed to have the plurality of connecting terminals formed a single metallic plate and connected to the stack of the semiconductor modules, thus causing the distance between the adjacent connecting terminals of the bus bar to be decreased with a decrease in distance between adjacent two of the semiconductor modules. The decrease in distance between the adjacent connecting terminals of the bus bar made of the single metal plate will restrict the size of each of connections of the connecting terminals. This results in a lack of the connections of the connecting terminals to the connecting terminals of the semiconductor modules.
The above problem may be solved by use of a stack of bus bars which are formed by a plurality of metallic plates. For instance, a bus bar stack is formed which is made up of a plurality of bus bars and has connecting terminals adjacent ones of which extend from the different bars of the bus bar stack. This permits the distance between the adjacent connecting terminals to be increased to widen the connections of the connecting terminals.
However, the inductance of semiconductor modules which are joined to the outer two of the stack of the bus bars is different from that of semiconductor modules which are joined to the inner two of the stack of the bus bars. This arises from a difference in effect of mutual inductance between the bus bars joined to the semiconductor modules. The surge voltage on the whole of the power converter depends upon the highest inductance. A problem is, therefore, encountered in that the difference in inductance between circuits of the semiconductor modules, therefore tends to undesirably increase the inductance of the whole of the power converter.
The invention was made in view of the above problems to provide a power converter which decreases a variation in effect of the mutual inductance among a plurality of semiconductor modules, thereby decreasing the inductance of the whole of the power converter.